The present invention relates to a leveling system for a vehicle, and more particularly to a valve body for distributing air to suspension elements.
Conventional leveling systems are installed in a wide variety of vehicles ranging from passenger cars to semi-trucks and semi-trailers. The larger leveling systems typically include pneumatic suspension elements, such as shocks or air springs, that can be inflated or deflated to control the height of the frame with respect to the axle. For example, on semi-trailers, heavy loads can cause a suspension to sag, thereby decreasing the distance between the frame and the axle. Accordingly, the ride height of the trailer, that is, the distance between the trailer bed and the ground, may be reduced. In conventional leveling systems, the ride height of the trailer may be adjusted by inflating or deflating the pneumatic suspension to compensate for the load. Specifically, when the ride height of a trailer has been affected by a heavy or light load, the suspension elements can be inflated or deflated to return the trailer to the desired ride height.
In leveling systems of the prior art, the height of the suspension is controlled by mechanical height control valves including a valve assembly and a valve body. The valve assembly senses the fluctuations in the ride height due to loading and controls the inflation/deflation of the suspension elements through the valve body. Typically, the valve body is located within the leveling circuit between a source of compressed air and the suspension elements. During operation, the valve body typically is in a neutral or “closed” mode. Accordingly, air cannot enter or leave the leveling circuit. However, due to fluid communication between suspension elements on opposite sides of the vehicle via the valve body, air may flow from a left side element to a right side element when the left side element is excessively loaded—this is called “side-to-side” air transfer. Obviously, air may flow from right to left when the right side is excessively loaded as well.
Illustrated in FIG. 1 is an uneven loading situation resulting in side-to-side air transfer. A vehicle 110 traversing a corner has a tendency to tilt or roll outward away from the “center” of the corner, due to centrifical force. During this tilting action, the right side elements 104 are excessively compressed by the load being shifted outward. Due to the fluid communication between the left 102 and right 104 side suspension elements, air is forced from right side suspension elements 104, travels through the valve body 108, and into the left side suspension elements 102. As a consequence, the left side suspension elements 102 extend and exacerbate the tilt or roll of the vehicle. Further, given the advent of larger airflow lines used in conventional leveling circuits to promote quicker inflation/deflation of air suspension elements, side-to-side air transfer is substantially increased.
Illustrated in FIG. 2 is a valve body 115 of the prior art that attempts to correct side-to-side transfer of air by placing a passive restrictive element 112 within the valve body 115. Although the use of the restrictive element does limit the side-to-side transfer of air A during cornering, it creates a variety of problems. First, the restrictive element restricts (a) dumping of air from the suspension elements, through the dump port 122 during deflation, and (b) injection of air into the valve body 115 via the supply port 126, and consequently into the suspension elements, during inflation. Second, dirt or debris accidentally entering the interior portion of the valve body, may become lodged between the restrictive element and the valve body to substantially impede airflow through the valve body. Moreover, to remove the debris, the valve body must be detached from the valve assembly.